Typical fans for moving air have a multiple number of blades fixed rigidly to a hub and surrounded by a ring to produce air flow when rotating. The usual problems with these fans, especially ones of large size, are (1) axial deflection, and (2) the stress level under centrifugal loading. Axial deflection of the fan is undesirable for reasons of interference with other components as well as for aerodynamic and aeroacoustic reasons. High blade stresses can lead to catastrophic failure of the fan. In conventional fan configurations, to add strength to the fan, the chord length is increased to fix the tip to the surrounding ring. These configurations add material to the outermost radial sections of the blade in order to achieve increased strength. However, the added mass contributes to excessive axial deflection.
Accordingly, there is a need to provide a fan in which axial deflection is minimized and the stresses are low while producing very high flow rates.